This work examines the relationship between whole kidney volume and renal function. It is also concerned with those factors which determine whole kidney volume, such as the compliance of the kidney and intrarenal pressure. We have found that at increased renal volume renal function deteriorates, and we propose to explore this phenomena further, and to find ways to control changes in renal volume and thereby prevent renal functional impairment. A secondary effort of this research program is to examine the factors which control immune complex uptake by the various capillary beds of the body. We have devised a means to measure the fractional uptake of immune complexes by injecting the immune complexes simultaneously with a marker of blood flow (microspheres) and a marker of intravascular volume (radiolabelled red cells). In this work we propose to determine the factors which determine immune complex deposition, and how this can be modified by pharmacologic means.